<ul class="nav">
  <li class="nav-item">
    <a class="nav-link" href="/">首页</a>
  </li>
  <li class="nav-item">
    <a class="nav-link" href="/admin">后台首页</a>
  </li>
  <li>
    <a class="nav-link" href="/admin/category">分类列表</a>
  </li>
</ul>